In recent years, along with advances in road maintenance and enhanced performance of vehicles, improvement in noise performance while achieving a high level of both dry performance and wet performance when driving at high speeds has become strongly desired for pneumatic tires.
Guaranteeing drainage by forming, on a tread surface of tires, main grooves extending in a circumferential direction as well as lug grooves and sipes extending in a width direction is normally performed as a method for improving wet performance. However, there is a problem that it is difficult to guarantee steering stability on dry road surfaces by such a method since the rigidity of land portions formed on the tread surface decreases. Moreover, there is also a problem that this decrease in rigidity simultaneously results in the deterioration of noise performance.
Many conventional measures for improving noise performance while achieving a high level of performance in both dry performance and wet performance include specifying the shape and position of lug grooves after specifying a mounting direction of a tire on a vehicle have been proposed. However, among these proposals, some of the tires have a problem of insufficient running performance when turning on dry road surfaces since the lug grooves formed in the land portions are positioned in the ground contact region open to the main grooves on the vehicle outer side. These lug grooves formed in the land portions positioned in the ground contact region opening to the main grooves on the vehicle outer side also simultaneously cause the problem that it is difficult to control noise performance as a result of the emission of pattern noise to the vehicle outer side. Other tires have difficulty in suppressing the generation of pattern noise or the dispersion thereof to the outside since the lug grooves are provided in the land portions on both shoulders in the ground contact region. There is thus a problem that noise performance deteriorates.